1. Field of the Invention
The present invention generally relates to electro-optical countermeasures and more specifically, to a technique and device for an automated determination of the laser threat status and the resulting insertion, retention, or removal of an appropriate filter in the forward looking infrared (FLIR) viewing devices' optical train.
2. Description of prior Art
The majority of current forward-looking infrared (FLIR) sensors are equipped with a filter wheel or sliding filter set for protecting the sensor from threat laser systems. The filters are mounted either in a rotating wheel or in a sliding mechanism, and in the best designs are tilted from the normal to reduce retroreflections. The filter sets normally are comprised of a "clear" filter which is normally in place, and several spectrally discriminating rejection filters. These filters are inserted under manual control by the operator (either slid into place with a sliding mechanism or rotated into place with a filter wheel) when the presence of a threat becomes apparent. One concern with the current schemes is how to determine when the laser threat status has begun, and when it is safe to remove the filter again. The use of the internal FLIR Focal Plane Array (FPA) for threat detection suffers from the serious pitfall that once a protective filter has been engaged, in most instances the system can no longer detect the threat.
While the prior art has reported using manual filter techniques none have established a basis for a specific apparatus that is dedicated to the task of resolving the particular problem at hand. What is needed in this instance is an automated determination of the laser threat status and the resulting insertion, retention, or removal of an appropriate filter in the FLIR's optical train.